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I'm looking for a circuit for a switch that can be activated by a standard laser poin

Discussion in 'LEDs and Optoelectronics' started by fazil abdulla, Feb 13, 2011.

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  1. fazil abdulla

    fazil abdulla

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    Feb 13, 2011
    I'm looking for a circuit for a switch that can be activated by a standard laser pointer and nothing else. I know I could probably buy some very expensive filters to only let laser light pass through, but I'd prefer something that uses a phototransistor or photodiode that can adjust sensitivity and tune to the proper frequency and or wavelength. Anyone have any ideas?
     
  2. Resqueline

    Resqueline

    2,848
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    Jul 31, 2009
    It can't be done with the criteria you're putting forth there, except for the sensitivity part; that's the only viable thing, along with filters.
    There's nothing uniqe about laser light that would allow an optical filter to pass only that and not a portion of white light.
    Phototransistors/diodes can't be tuned to an exact wavelenght (or optical frequency if you will) like you have in mind there.
    The only reliable way would be to modulate the laser diode at a specific frequency - like IR remote controls do (32-35kHz).
    Otherwise a combination of optical filters, timing, directional, and intensity discrimination could make it relatively immune to accidental activation.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    I guess you could surround a central detector with 6 similar detectors and have logic set up so that the circuit only triggers if only a single sensor (or perhaps only the central one) sees bright light. You could vary the spacing of the sensors to allow for the maximum spot width.

    You would still be able to trigger it with other light sources, but it wouldn't be easy.

    If you are able to modify the laser light source, then modulating the beam and detecting the modulation would be more rugged (again, you could modulate a LED to mimic that, but not accidentally one presumes.
     
  4. Bucky Crisp

    Bucky Crisp

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    Apr 15, 2011
    I am also in need of a hand held laser switch actuator. I have found a patent and diagram which looks to be exactly what I need but since I'm not an electronic whiz I need some help. Anyone interested, please respond to my post.
     
  5. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Well, post a link to the patent then, perhaps..
     
  6. Bucky Crisp

    Bucky Crisp

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    Apr 15, 2011
    laser pointer actuated switch

    I found an invention which will fulfill my requirement to open or close a switch with a hand held laser pointer. I found the invention patent by using Google. The number of the patent is 6690003. I have tried to contact the patent owner for more info, but have had no response. I have also talked to a number of electronic suppliers with no success. If any one is interested in helping me on this project, I would be very appreciative. Sorry I don't have more information at this time but am willing to follow any leads.
    Thanks, Bucky
     
  7. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    That "invention" has to be one of the simplest and most useless ones I've seen. Sure, it'll work, but it suffers from all the drawbacks already discussed here.
    I'm surprised it was worthy of a patent, and judging by its exceeding simplicity it could've been thought up by a kid.

    1: To be relatively immune to false triggerings it'll need an expensive optical filter.
    2: You need to have a line of sight to it. (Not always possible, making it vulnerable to be non-functional.)
    3: You need to aim the laser dead accurate. (Annoyingly inconvenient, and imagine if you own a cat..)
    4: It can still be activated by other light sources. (Insecure.)

    That being said, except for the filter you can build it yourself for a few bucks (or even for free if you got some scrap hardware around) and hardly any knowledge.
     
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